Indirect thermal storage solar heating system consists of flat plate solar collectors, auxiliary heat source, heat storage tank, plate heat exchanger, circulation pump,heating ends and other components. The mathematical model of the flat collector, plate heat exchanger, and heat storage tank were established. Combining to the model of other components, the simulation of the indirect thermal storage solar heating system was finished. Taking the heating system of a residential building in Lhasa as an example, through the calculation of the heat storage process within the entire heating season, it resulted the hourly heat collection efficiency, the hourly water temperature and the hourly heat collection, as well as the daily average heat collection efficiency, the daily heat collection, the daily tank final temperature, the daily auxiliary heat and the total auxiliary heat.